"We are taking all possible steps to reduce the detainee population at Guantanamo and to close the detention facility in a responsible manner that protects our national security," US Secretary of State John Kerry said in a statement.

Mr Ghereby was approved for transfer under a presidential executive order from 2009. US security services decided it was no longer necessary to hold Mr Umar last August.

Image copyrightUS Department of JusticeImage caption
A total of 780 men have been held at Guantanamo Bay since 2002, the vast majority without charge or criminal trial

Mr Obama promised to close Guantanamo in 2009 and wants to transfer the remaining detainees to their home countries or to US military or civilian prisons.

In February, he said the prison was "contrary to US values" and undermined the country's standing in the world.

But Congress remains deeply opposed to terror suspects being held on US soil.

A total of 780 men have been held at Guantanamo Bay since 2002, the vast majority without charge or criminal trial.

Of those who have left the prison, nearly 100 have been resettled across 26 countries, others have been freed and one man has been sentenced to life in prison after standing trial in a US civilian court.